1. Technical Field
Embodiments relate to detecting the degradation of a semiconductor device and detecting the degradation of an integrated circuit having the semiconductor device. In particular, embodiments relate to detecting the degradation of a semiconductor device such as a metal oxide semiconductor (MOS) transistor caused by stress generated in the operation of the semiconductor device, and detecting the degradation of an integrated circuit having the semiconductor device.
2. Description of the Related Art
Semiconductor devices have become highly integrated, requiring minute patterns and/or wirings to ensure a high degree of integration. The semiconductor device generally includes a MOS transistor as a unit element. While operating the semiconductor device, the degradation of the MOS transistor can occur due to stress generated in the operation of the semiconductor device. When the semiconductor device operates continuously for a long time, the semiconductor device can become degraded such that the semiconductor device does not satisfy desired user requirements.
Accordingly, it is necessary to detect the degree of degradation of the semiconductor device in the operation of the semiconductor device. To detect the degradation of the semiconductor device, the degradations of individual unit elements in the semiconductor device can be detected. Then, the effect of the degradations of the unit elements relative to the degradation of the semiconductor device is analyzed. When the effect of the degradations of the unit elements relative to the degradation of the semiconductor device is analyzed, the operation characteristics and the reliability of the semiconductor device can be improved.
Generally, the main factor causing the reliability degradation of the MOS transistor can be recognized as hot carrier injection of the MOS transistor. While continuously operating the MOS transistor, electrons and/or holes having high energy are injected to a gate insulation layer of the MOS transistor. The electrons and/or holes are caused by the high electric field generated adjacent to the drain region of the MOS transistor. Since the gate insulation layer has numerous trap sites, the injected electrons can be trapped into the trap sites in the gate insulation layer. Thus, the characteristics of the gate insulation layer can be changed by the electrons trapped therein thereby deteriorating the performance of the MOS transistor. When the performance of the MOS transistor has deteriorated, the semiconductor device can be degraded. For example, the RC delay of the semiconductor device can be increased and the lifetime of the semiconductor device can be reduced.
In addition, the degradation of the MOS transistor can occur based on other factors besides the hot carrier injection, such as a strained offset stress degradation, a FN stress degradation or a negative bias temperature instability (NBTI) degradation. Further, the degradation of the MOS transistor caused by other factors can become important in accordance with the high integration of the semiconductor device. Hence, the degradation of the MOS transistor caused by other factors, are considered when the degradation of the MOS transistors is detected. The strained offset stress degradation of the MOS transistor can be caused by drain voltage induced stress while the MOS transistor is turned off. Further, the FN stress degradation can occur when the drain voltage is not properly applied to the MOS transistor and the MOS transistor is turned on. Therefore, to detect the degradation of the semiconductor device, each of the individual degradation mechanisms caused by the stress can be investigated. The reliability of the semiconductor device can be guaranteed by analyzing the degradation mechanisms of the individual unit elements.
However, the mutual effect among the individual degradation mechanisms cannot be properly considered when the degradation of the semiconductor device is predicted. Thus, the degradation of the semiconductor device cannot be correctly predicted based on the individual degradation mechanisms of the unit elements. Particularly, the degradations of the unit elements in the semiconductor device can simultaneously occur through the individual degradation mechanisms while operating the semiconductor device. Therefore, the reliability and operation characteristics of the semiconductor device cannot be precisely detected though the individual degradation mechanisms of the unit elements in the semiconductor device.